Admixtures have been added to cementitious mixtures to improve their properties. Better flow characteristics of the cementitious mixtures prior to setting increases density of the casting, reducing undesirable voids, and reducing the water requirement increases the strength of the concrete. Delaying the setting time is also desirable in some circumstances, particularly in warmer climates.
Lignin and/or lignin related compounds have traditionally been used as admixtures for cementitious mixtures. However, lignin has recently become quite expensive, and is in short supply. Other substitutes have been tried, but have been found not to perform as required, and/or not been cost effective. Substitutes can be, and often are, added to lignin based admixtures, but this practice, though extending the lignin base, results in less than maximum improvement obtained with unadulterated lignin based admixtures and/or is expensive. Molasses is often or sometimes used as a substitute for lignin. However, it is generally accepted that molasses does not perform as required by itself and is not suitable itself as a water reducing admixture to cementitious mixtures. Against this background, it has been surprisingly found that dunder performs adequately as an admixture for cementitious mixtures, and if modified in accordance with the invention described hereinafter, obtains equal or superior results when compared with ordinary lignin. In this specification, unless the context requires otherwise, dunder includes any residuum obtained after distillation of molasses or sugar product such as vinasse and the like. In this specification, unless the context requires otherwise, the terms “cementitious mixture” and “concrete” are taken to include concrete, shotcrete, mortars, grouts and similar cementitious compounds including mine tailing (backfill). Generally, the term cement refers to a compound which is soft when first prepared but sets or hardens. In the case of cementitious mixtures, cement becomes plastic after the addition of water, after which the mixture sets. In this specification, unless the context requires otherwise, the term “cementitious mixture” refers to the workable liquid which can solidify to form mortar or concrete. In this specification, the term “Portland cementitious mixture” refers to a combination of cementitious materials which consist of the active ingredients and binders and to which sand, aggregate and/or other additives may be added with water to form a cement paste, mortar or concrete.
The present invention aims to provide an admixture for cementitious mixtures, and a method of forming cementitious mixtures, which alleviate at least one of the shortcomings of the prior art, or at least to provide an alternative to currently used admixtures for cementitious mixtures. Other aims and advantages of the invention may become apparent from the following description.